Electromagnetically-controlled hydraulic governor for electric and other arc furnaces



g- 1930. L. TAGLIAFERRI' ELECTROMAGNETICALLY CONTROLLED HYDRAULICGOVERNOR FOR ELECTRIC AND OTHER ARC FURNACES Filed Dec. 12. 1928 3Sheets-Sheet l evverv TJQ 6, 1930. L. TAGLIAFERRE 13 ELECTROMAGNETIGALLYCONTROLLED HYDRAULIC eovnnuoa FOR ELECTRIC AND OTHER ARC FURNACES FiledDec. 12 1928 3 Sheets-Sheet 2 aaenala i E ,MM

Aug. 26, 1930. TAGUAFERRI 1,774,213

ELECTROMAGNETICALLY CONTROLLED HYDRAULIC GOVERNOR FOR ELECTRIC AND OTHERARC FURNACES Filed Dec. 12, 1928 3 SheetsShe.et 3

Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE LEONE TAGLIAFERRI, OFGENOA, ITALY Application filed December 12, 1928, Serial no.

The present invention refers to an electromagnetically controlledhydraulic governor for electric arc furnaces.

In the known governors of this kind, on

account of the instability of the arc the controlling means always enterinto action too late so that considerable fluctuations of the load takesplace in the current network which are liable to cause damage to theinstallation. In order to prevent the unavoidable peaks in the loadexceeding a certain inadmissible limit, it has until now been necessaryfor the safety of the installation for the average current strength ofthe arc to be kept at a comparatively low value.

Moreover, the known governors, on account of their delicate constructionare not suitable for the extremely rough service connected with theoperation of an electricarc furnace. The object of the present inventionis to remove these disadvantages and to provide a governor for furnaceshaving an are, by means of which a quick and safe control is obtainedand in which the automatic regulation is entirely independent of themanual control.

The invention is illustrated by way of example in the accompanyingdrawings in which:

Figure 1 shows a general arrangement of a governor according to theinvention employed in connection with an electric furnace and a diagramof the electric conductors.

Fig. 2 is a sectional detail view of the water 3 cylinder under pressurewith vertical iston. Fig. 3 is a sectional detail view of a nown elasticsuspension.

Fig. 4: is a vertical'sectional middle view across the upper part of thedifferential pis- 4 ton with control valve on an enlarged scale.

Fig. 5 is a top view of the governor with the cover taken off.

Fig. 5 is a side elevation of an armature control shown in plan view inFig. 5.

Figs. 6, 7 and 8 show different positions of the movable armature andvof the control valve with a section along the line o-b in Figure 4.

In these figures 1 is the electrode of the 00 electric furnace, fastenedon the movable 325,535, and in Germany December 12, 1927.

support 2, slidably fastened in its turn by means of the slide 3 upon arail 5 secured to the furnace. Upon the slide 3 is jointly connected at6 the piston 7 of the hydraulic lifting cylinder 8 which at its lowerend is jointly connected at 9 upon the bearing 10 rigidly secured to thefurnace. The hydraulic lifting cylinder 8 is single acting; the waterunder pressure coming from the control cylinder 11 enters the cylinder 8through a cock 12. Y i

The plant providing the water under pressure includes an electromotor13, operating a rotary pump 14. This draws water from the receptacle 15and forces it through the conduit 16 into the accumulator 17 into whichprojects one end of the water outlet pipe 18, the other end of which isconnected with the hydraulic control cylinder 11 The accumulator 17 isprovided for the purpose of damping the fluctuations in the pressurewhich may arise during the operation and also to allow the electrodes inthe furnace to be still lifted should the pump 14.- be put out ofoperation. In this case a nonreturn valve will be closed in'the suctionpipe of the pump and the electrode will be lifted by the ressure in thereceptacle.

The distri uting device for water under pressure or main servo-motorcomprises a cylinder 11 within which moves the vertical piston 19 whichcan be displaced manually y the stirrup 20; the cam 21 and the handwheel 22.

In the osition indicated in the drawing, the distri uting disc 19 of thevertical pistoo 19 in its extreme upper position: in

this position of thepiston the water, admitted through the pipe 18,after having passed the chamber 23, can pass to the pipe 24 and entersthrough the open cook 12 into the hydraulic lifting cylinder 8, so as tolift the piston and with it the electrode. By the 4 rotation of the cam21, the vertical piston is lowered under the ressure of the spring 32,until the distributing disc 19' for a determined position, perfectlycloses the inlet of the pipe 24;, whereby the electrode becomesstationary. By further rotating the cam 21 the vertical piston 19 ismoved further down,

so that the pipe 24 is put into communication through the chamber 25withthe discharge pipe 26. The piston 7 now descends under the weight 'ofthe electrode 1, the support 2 crease in the possibilities of regulatingand this is obtained by a rotation of the piston within the cylinderwhen the apparatus is being assembled and adjusted initially and bymaintainin the same pressure and the same axial position of the pistonduring the working of the apparatus.

The manual regulation is therefore simply effected by the rotation ofthe handwheel 22. 27 is a casing which is connected by the columns 28with the hydraulic cylinder 11. 29 is a differential piston which passesthrough the bottom of the casing 27 and the thickened upper end 29 ofwhich moves within a cylindrical bore 30in the bottom of the casing 27.31 is a threaded shank of the differential piston, which is rigidlyconnected with the piece 20. 32 is a helical spring, which surrounds thedifferential piston and which bears at one end against the bottom of thereceptacle 27 and at the other end against a disc 33 threaded upon theshank 31. The differential piston is therefore also rigidly connectedwith the vertical hydraulic piston. The head 29 of the differentialpiston moves within the cylindrical bore 30 of the casing 27 and is supplied with a number of axially extending ports 35, each of whichcommunicates through a small radially directed hole 36 with a chamber 37in the interior of the head of thediiferential piston. In a cylindricalbore 38 (Figure 4) in the head of the differential iston is arranged thedistributing valve 39 of the auxiliary distribution system so as to berotatable through a small angle. The valve 39 is of special constructionand is fastened by means of a ring 40, a point 41, a threaded pin 42upon the bracket 43 fastened to the casing 27 by a resilient bearing ofknown construction as illustrated in Figure 3. Upon the shaft 44 of thevalve 39 is arranged a movable armature 45, belonging to theelectromagnet 46. the stationary armature of which is arranged on thecasing 27. The Winding 47 of the magnet is connected with the secondarycircuit 48 of the transformer, the primary circuit of which is connectedin series in the phase conductor 49, which connets the furnace feedingtransformer with the electrode. Within the valve body 39 are arrangedwithin the four axially running ribs 50, the longitudinal ports 51, eachof which, in a certain position, as shown in Figure 7, registers withone of the radial holes"36 in differential piston 29. At the lower endof the cylindrical bore 30 of the casing is provided an opening whichcommunicates through a pipe 52 with the receptacle 53. In thisreceptacle there. exists a certain over pressure to compensate forfluctuations in pressure and to allow, should the oil pump stop, thedifferential piston to be raised, whereby the electrode is also liftedby the servo-motor. The receptacle 53 is connected with the oil pump 54operated in its turn by the motor 13. If the longitudinal grooves 51 ofthe valve 39 are in register with the radially extending holes 36 in thedifferential piston 29, the oil from the pump 54, which may beconveniently regulated in quantity by the adjustment of the cook 55, canflow into the interior of the casing 27 and return by the discharge pipe56 into the oil receptacle 57 connected with the oil pump 54. As bymeans of this connection no oil pressure can be generated in the chamber58, the spring 32 keeps the differential piston in its lowest position;it is understood that when the automatic control is to be used the cam21 will have to be turned to a position which is displaced through 180with respect to the position shown in the drawing.

By the rotation of the valve 39 through a small angle the ribs arebrought into a position in which they close the radial holes 36 in thedifferential piston. .As the oil is now prevented from passing out, itis collected in the chamber 58 and presses on the head of thedifferential piston. This overcomes the force of the spring 32 and thepiston is lifted for such an amount as to push against the stops 59which limit the upper extreme position of the differential piston. Therotation of the valve 39 which is rigidly connected with the movablearmature 45 of the electromagnet is produced by the varition in theintensity of magneticforce in the armature, this flux density beingproportional to the current strength in the conductor which leads thecurrent from the transformer to the furnace. 60 are two helical springssymmetrically arranged with respect to the axis of the movable armature45, which springs by exerting a'tangential opposite effort on this.armature, prevent the formation of friction between the contact surfacesof the valve 39 and the differential piston 29. These springs aredirectly connected at one end with the movable armature 45 by means ofpins 61 and at the other end with a bell crank lever 62 which has itsfulcrum at 63 upon the bracket 64 and the shorter arm of which bearsagainst the upper surface of the differential piston. This leverarrangement has for its object to hold the movable armature 45 againstthe end of the lever 65 and also to control the hunting oscillations ofthe controlling parts.

In the inoperative condition, that is to say in the condition inwhichthe furnace is not connected to the source of suppl the movable armature45, as illustrated in igures 5 and 6- bears under the effect of theopposite springs against the end of a lever 65, which is fastened uponthe shaft 66 supported on the casing 27. Upon the shaft 66 is alsofastened a. lever 67 on the end of which is provided the movablearmature 68 which belongs to the electromagnet 69, the winding 7 0 ofwhich is connected across the supply conductors of the furnace. If theinstallation should remain without tension, that is to say, is placed inthe zero tension condition, it will be necessary that the electrodes arelifted from the metal bath. In this case the armature 68 drops from thetensionless electromagnet 69 and provocates the movement of the lever65, so as to allow to the armature 45 to be displaced as shown in Fig. 6and to close the )i1 passage. In Figure 6 is indicated the position ofthe movable armature 45 for which the furnace and therefore the twoelectromagnets are without current. In this position of the armature thegrooves 51 of the valve 39 do not register with the radial holes 36 inthe differential piston and the armature 45 bears against the end of thelever 65. If the pump 54 is now put into operation, pressure is producedin the chamber 58 by the admission of oil, which pressure lifts thedifferential piston and with it the vertical piston of the mainservo-motor. As soon as the furnace is connected to the supply, thearmature 68 is attracted by the electromagnet 69. The lever displacesthe armature 45 into the position shown in Figure 7 for which thegrooves 51 of the valve 39 register with the radial holes 36 inthedifferential piston. The latter drops and with it the electrode untilthe electrode touches the charge formed.

The electromagnet 46 is now energized and the movable armature 45 andthe valve 39 will rotate under the influence of the magnetic attraction,for instance through an angle B and the parts will then occupy theposition shown in Figure 8.

In this position of the movable armature 45 the grooves 51 in the valve39 no longer register with the radial holes 36 in the differentialpiston. Pressure is again produced under the piston, whereby theadmission of water under pressure takes place in the hydraulic liftingcylinder, thus lifting the electrode to strike the are.

As the lifting of the electrode continues the length and therefore theresistance of the are are increased; the current strength decreases,whereby the movable armature 45 under the influence of the springs 60returns to its original position shown in Figure 7.

During the practical operation of the installation a certain conditionof equilibrium is established between the current strength and theposition of the armature, so that the vertical piston 19 is onlydisplaced by a small amount from its middle normal working position andonly rarely reaches its extreme positions in which the maximum admissionand discharge of water occurs. In these extreme positions the most rapidregulating action for he arc can occur, as the water in the completedlyopen pipes will assume the highest spee The feed device is soestablished that one pump is suflicient for the water feed and one forfeeding the oil to feed at the same time the three electrodes of threephase current furnaces.

A regulating resistance 71 is connected in parallel with the winding 47of the electromagnet 46 in order to enable the current strength to beregulated within the wide limits on which the automatic governor has towork.

I claim as my invention:

1. Arc furnace comprising in combination, an electrode, an electriccircuit for said electrode, a liquid pressure operated servo-motor toproduce the motive-power for said electrode, said servo-motor comprisinga vertical cylinder, a recessed vertical piston valve with a Wedge-likedistributing disk between the end disks so as to operate upon movementthe increasing pressure supply to the lifting cylinder, the maintainmentof the pressure supply or the pressure discharge, a spring pressed stemrigidly attached to the said piston .valve, a hand-controlled camcoacting with abutment means rigidly connected with said stem so toaxially displace the piston valve, a hollow differential piston bodyattached to the upper end of said stem, passages in this body leadingaxially from its bottom and then radially to a valve seat, a suspendeddistribution valve placed in the cavity of the piston body and incorrespondence with said seat and provided with longitudinal grooveswhich can be made to register with the radial holes of the piston, acylinder body for the said piston body, a tight casing in which the topend of said cylinder opens, a feed pipe for an auxiliary pressure fluidopenin into the bottom part of said cylinder, a uid discharge pipeopening into the tight casing connected with the cylinder body andautomatically electrically controlled means for varying the angularposition'of the said distributing valve, so that a small angulardisplacement thereof is suflicient to alternatively establish or checkthe passage of the said auxiliary pressure liquid.

2. Arc furnace comprising in combination, an electrode, anelectriccircuit for said electrode, a liquid pressure operated servo-motor toproduce the motive power for said elec trode, said servo-motorcomprising a vertical cylinder, a recessed vertical iston valve havinend disks and a wedge-1i e distributing disk between the end disksthereof, a pressure pump, a pressure accumulator in- -to a valve seat ofa yieldable suspended distribution valve placed in the cavity of thepiston body and in correspondence with said seat and provided withlongitudinal grooves adapted to register with the radial portions of theports, a cylinder body for the said a piston body, a tight casing inwhich the top end of said cylinder opens, a feed pipe for an auxiliarypressure fluid opening into the bottom part of said cylinder, a fluiddischarge pipe opening into the tight casing connected with the cylinderbody, a pressure pump and a pressure accumulator inserted in theauxiliary pressure fluid circulation, a movable armature of anelectromagnet symmetrically arranged and carried by the suspendeddistribution valve, in which the winding of the magnet is connected withthe secondary circuit of the transformer, the primary circuit of whichis connected in series with the furnace feeding phase conductor.

3. Arc furnace comprising in combination, an electrode, an electriccircuit for said electrode, a liquid pressure operated servomotor toproduce the motive power for said electrode, this servo-motor comprisingwithin a vertical cylinder a recessed vertical piston valve having enddisks, a wedge-like distributing disk between the end disks of thepiston, a pressure pump and a pressure accumulator inserted in themotive power fluid of the electrode, a spring-pressed stem rigidlyattached to the piston valve, a hand controlled rotating,cam coactingwith a stirrup rigidly connected with said stem, a hollow differentialpiston body attached to the upper end of said stem, passages in thisbody leading axially from its bottom and then radially to a valve seatof an elastically suspended distribution valve placed in the cavity ofthe piston body and in correspondence with said seat and provided withlongitudinal grooves adapted to register with the radial passages of thepiston, a cylinder body for the said piston body, a tight casing inwhich the top end of said cylinder opens,

' a feed pipe for an auxiliary pressure fluid opening into the bottompart of said cylinder, a fluid discharge pipe opening into the tightcasing connected with the cylinder body, a pressure pump and a pressureaccumulator inserted in the auxiliary pressure fluid circulation, amovable armature of an electromagnet symmetrically arranged and carriedby the suspended distribution valve, two opposite helical springssymmetrically arranged with respect to the axis of the movable armaturewhich are in equilibrium for a determined current strength, with theattractive force exerted on the armature by the magnetic flux of force,the armature when under no voltage adhering against a movable stop atclosed passage of the auxiliary liquid, whereby by the insertion of thetension of the current the'armature secures the opening of the passageand during fluctuations of current the valve is alternatively displacedfrom the open to a new closed position and vice versa.

4. Arc furnace comprising in combination, an electrode, an electriccircuit for said electrode, a liquid pressure operated servomotor toproduce the motive power for said electrode, this servo-motor comprisinga vertical; cylinder, a recessed Vertical piston valve having end disks,a wedge-like distributing disk between the end disks of the piston forincreasing the sensitiveness of regulation, a pressure pump and apressure accumulator inserted in the motive power fluid of theelectrode, a spring pressed stem rigidly attached to the piston valve, ahand controlled rotating cam coacting with a stirrup rigidly connectedwith said stem, a hollow diflerential piston body attached to the upperend of said stem, passages in this body leading axially from its bottomand then radially to a valve seat of an elastically suspendeddistribution valve placed in the cavity of the piston body and incorrespondence with said seat and provided with longitudinal grooveswhich can be made to register with the radial holes of the piston, acylinder body for the said piston body, a tight casing in which the topend of said cylinder opens, a feed pipe for an auxiliary pressure fluidopening into the bottom part of said cylinder, a fluid discharge pipeopening into the tight casing connected with the cylinder body, apressure pump and a pressure accumulator inserted in the auxiliarypressure fluid circulation, a movable armature of'an electromagnetsymmetrically arranged and-carried by the suspended distribution valve,two opposite helical springs symmetrically arranged with respect to theaxis of the movable armature attached at one end to said armature and atthe other ends each to the arm of a bell crank lever, the other arm ofwhich presses against the up or face of the diflerential piston with theo jects of holding the movable armature against the end of a lever andalso controlling the hunting 0s- ,cillation of the controlling parts.

5. Are furnace comprising in combination, an electrode, an electriccircuit for said electrode, a liquid pressure operated servomotor toproduce the motive power for said electrode, said servo-motor comprisinga pressure pump and a pressure accumulator inserted in tlie motive powerfluid of the electrode, a spring pressed stem rigidly attached to thepiston valve, a hand-controlled rotating cam coacting with a stirruprigidly connected with said stem, a hollow difierential piston bodyattached to the upper end of said stem, passages in this body leadingaxially from its bottom and then radially to a valve seat of anelastically suspended distribution valve placed in the cavity of thepiston body and in correspondence with said seat and provided withlongitudinal grooves which can be made to register with the radial holesof the piston, a cylinder body for the said piston body, a tight casingin which the top end of said cylinder opens, a feed pipe for anauxiliary pressure fluid opening into the bottom part of said cylinder,a fiuid discharge pipe opening into the tight casing connected with thecylinder body, a pressure pump and a pressure accum ulator inserted inthe auxiliary pressure fluid circulation, a movable armature of anelectromagnet symmetrically arranged and carried by the suspendeddistribution 'valve, two opposite helical springs symmetrically arrangedwith respect to the axis of the movable armature attached at one end tosaid armature and at the other ends each to the arm of a bell cranklever, the other arm of which presses against the upper face of thedifferential piston with the objects of holding the movable armatureagainst the end of a lever and also controlling the hunting oscillationof the controlling parts, a movable stop operated by the movablearmature of an electromagnet, the windings of which are in connectionwith the tension of the installation that if the furnace is Withoutvoltage the stop keeps the movable armature of the passage controllingvalve in an 0 en position, thus lifting the electrode, an if the furnaceis put under voltage the armature of the zero voltage electromagnetdisplaces the movable armature of the passage controlling valve into aclosed position so as to lower the electrode.

In testimony whereof I have signed my name to this s cification. I

ONE TAGLIAFERRI.

